Description

strtol() and strtoll()

The strtol() function converts the initial portion of the string pointed to
by str to a type long int representation.

The strtoll() function converts the initial portion of the string pointed to
by str to a type long long representation.

Both functions first decompose the input string into three parts: an initial,
possibly empty, sequence of white-space characters (as specified by isspace(3C)); a subject sequence
interpreted as an integer represented in some radix determined by the value
of base; and a final string of one or more unrecognized characters,
including the terminating null byte of the input string. They then attempt
to convert the subject sequence to an integer and return the result.

If the value of base is 0, the expected form of the
subject sequence is that of a decimal constant, octal constant or hexadecimal
constant, any of which may be preceded by a + or -
sign. A decimal constant begins with a non-zero digit, and consists of
a sequence of decimal digits. An octal constant consists of the prefix 0
optionally followed by a sequence of the digits 0 to 7 only.
A hexadecimal constant consists of the prefix 0x or 0X followed by
a sequence of the decimal digits and letters a (or A) to
f (or F) with values 10 to 15 respectively.

If the value of base is between 2 and 36, the expected
form of the subject sequence is a sequence of letters and digits
representing an integer with the radix specified by base, optionally preceded by
a + or - sign. The letters from a (or A) to z
(or Z) inclusive are ascribed the values 10 to 35; only letters
whose ascribed values are less than that of base are permitted. If
the value of base is 16, the characters 0x or 0X may
optionally precede the sequence of letters and digits, following the sign if present.

The subject sequence is defined as the longest initial subsequence of the
input string, starting with the first non-white-space character, that is of the
expected form. The subject sequence contains no characters if the input string
is empty or consists entirely of white-space characters, or if the first non-white-space
character is other than a sign or a permissible letter or digit.

If the subject sequence has the expected form and the value of
base is 0, the sequence of characters starting with the first digit
is interpreted as an integer constant. If the subject sequence has the
expected form and the value of base is between 2 and 36, it
is used as the base for conversion, ascribing to each letter its
value as given above. If the subject sequence begins with a minus
sign, the value resulting from the conversion is negated. A pointer to
the final string is stored in the object pointed to by endptr, provided
that endptr is not a null pointer.

In other than the POSIX locale, additional implementation-dependent subject sequence forms may
be accepted.

If the subject sequence is empty or does not have the expected
form, no conversion is performed; the value of str is stored in
the object pointed to by endptr, provided that endptr is not a
null pointer.

lltostr() and ulltostr()

The lltostr() function returns a pointer to the string represented by the
longlongvalue. The endptr argument is assumed to point to the
byte following a storage area into which the decimal representation of value is
to be placed as a string. The lltostr() function converts value
to decimal and produces the string, and returns a pointer to
the beginning of the string. No leading zeros are produced, and no
terminating null is produced. The low-order digit of the result always occupies memory
position endptr-1. The behavior of lltostr() is undefined if value
is negative. A single zero digit is produced if value
is 0.

The ulltostr() function is similar to lltostr() except that value is an
unsigned long long.

Return Values

Upon successful completion, strtol(), strtoll(), atol(), atoll(), and atoi() return the converted
value, if any. If no conversion could be performed, strtol() and strtoll()
return 0 and errno may be set to EINVAL.

If the correct value is outside the range of representable values, strtol()
returns LONG_MAX or LONG_MIN and strtoll() returns LLONG_MAX or LLONG_MIN (according to
the sign of the value), and errno is set to ERANGE.

Upon successful completion, lltostr() and ulltostr() return a pointer to the converted
string.

Errors

The strtol() and strtoll() functions will fail if:

ERANGE

The value to be returned is not representable.

The strtol() and strtoll() functions may fail if:

EINVAL

The value of base is not supported.

Usage

Because 0, LONG_MIN, LONG_MAX, LLONG_MIN, and LLONG_MAX are returned on error and
are also valid returns on success, an application wishing to check for
error situations should set errno to 0, call the function, then check errno
and if it is non-zero, assume an error has occurred.

The strtol() function no longer accepts values greater than LONG_MAX or LLONG_MAX
as valid input. Use strtoul(3C) instead.

Calls to atoi() and atol() might be faster than corresponding calls to
strtol(), and calls to atoll() might be faster than corresponding calls to
strtoll(). However, applications should not use the atoi(), atol(), or atoll() functions unless
they know the value represented by the argument will be in range
for the corresponding result type.